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Part5 - Yocto terminology

Terminology -> metadata, recipe, configuration, class, layer

#yocto   #101  

Table of Content

Recipe#

A recipe is a set of instructions that is read and processed by the bitbake (file with .bb extension)

A recipe describes:
- Where to fetch source code
- Which patch to apply
- Configuration options
- Compile options
- Install
- License

Configuration#

Tell the build system what to build and put into the image (file with .conf extension)

Types#

  • Machine configuration option
  • Distribution option
  • Compiler tuning options
  • General Common configuration options
  • User options (local.conf)

Example machine config#

User local.conf we set the machine for example MACHINE ??= "qemux86-64"

This setting tell the system to load machine configuration option meta/conf/machine/qemux86-64.conf

Class#

Class files are used to share common functionality across recipes (file with .bbclsss extension)

Note

classes useally locate in classes directory inside the meta* directory

usage from recipe#

inherit classname

Layers#

A collection of related recipes.
layer isolate meta data according to functionality recipes are folders under layer folder

Note

name convention for layer meta-layername

name description
meta-poky Distro metadata
meta-yocto-bsp BSP metadata

BBLAYERS variable present in build/conf/bblayers.conf

show layers
bitbake-layers show-layers

Find a layer#

OpenEmbedded Layer Index

raspberrypi

ros2 layers

Image#

An image is the top level recipe
image define how the root filesystem is built , with what packages.

list all images
ls meta*/recipes*/images/*.bb

Packages#

A package is a binary file with name .deb, .rpm Packages are produces by recipe A signal recipe produces many packages. all recipe packages describe is PACKAGES variable